Manufacture of butadiene



June 19, 1945. y wl J, MATTOX 2,378,650 'y Y MANUFACTUREQF BUTADIENE I A File'daFebull, y1942 vf/@ACTION LSEPHPHTION B Z/TADIENE Patented June 19, 1945 f oNrrao' .sr-Afr duction of rubber. f

V'diable' quantities, ,theV system .by recycling, `carbon .this reason, it

` age'Cifraction :menenanon stepr as. PATENT MANUFACTURE oF u'rannaNE william J. Mami, chicago, nl.,

versa! Oil'Products Company, corporation of Delaware 'assignorto Uni- Chicago, lll., a

Applicationrebmry i1, 1942, serial-N0. 430,500

--11 claims. 101.2604680) This is" a continuation-impart of my Aevo-pend ing application Serial No. 343,976,1l1edvJu1yp31, 1940. i'. Y This invention relates to a precess for the manufacture .of'butadliene from" ractions. More specically, itis fncerned ent primarily upon processes for the production of butadieneand styrene since these two chem-v principal rawV materials for the proicals are the Therefore, processes Vwhich can produce butadiene charging materials are very much in need at the present time.'` Butadiene isl most commonly made by the dehydrogenation of. normal C4 hydrocar- Ybo'nsin the presenceof a catalyst. Whenever and isobutene are present in appreand fare allowed to build up in formationA bee'xcessive since these iso compounds -will notdehydrog'enate directly to butadiene.y For has been necessaryto' reduce the iso fraction ofv the C4 hydrocarbon charge ;to a ylow'valu'ein'order to preventbuildup.

"I have found that-by combining isomerization with'dehydrogenation, butadienev can bep'roduced with highyields from the ordinary C4 fraction present iny a refinery gas; natural gas, or the. like. process, the isobutene originally iaobutane drogenation of isobutane in the'dehydrogenation stepv is isomerized by a highly active catalyst comprising hydro'us silica composited. with hydrous alumina or hydrous zirconia. i The resulting normal butenes are then readily dehydrogenated Yto butadiene. By' this process, a higher ultimate yieldoi butadiene may be obtained from an averthan'from the conventional operation since iso' C4 hydroca bonsare alsol converted to butadiene; Furthermore, an expensive preemployed Vin the lconventional operation'toseparate iso from`normalfC4 hydro,- carbons is eliminated.' Y* e There are two ways in general inwhich my process may be operated. In the first method, a composite C4 fraction lis subjected to dehydrogenation with subsequent, .production of butadiene. Following the separation-of thefbutadiene from the reactiony products, the remainingC4 hydro- 'carbons are contacted with an isomerizationcatalyst attemperatures capable ot eifecting isomerizatlon of a substantiel part oithj-.isohntene Y l e y method for con-v y verting mixed C4 hydrogcarbons, both normal and iso, into vhigh yields of butadiene by :av` combinafromabundant and cheapv -stanual portion of to `normal butene. Ihe resulting product of isomerization containing a larg'eproportion of normal butenes isthen commingledwith the original charging stock and thecompositelmaterial again subjectedk to dehydrogenationV to 'produce buta-Y diene and more butenes.

Alternatively, the isomerizaton and dehydroi genation reactions may be effected in the same zone by employing catalysts which have not only deliydrogenatingl properties but, also olefin isomerizing properties. 'I'he butadiene thus formed may then be separated f-romthe reaction products and theremaining returned to the'dehydrogenating-isomerizing zone iegether with the r'aw feed to produce more butaene.

' In one speciiicembodiment the present inven.

tion` relates-to a'process. for; the production of butadiene froma C4 fraction composed of normal 'and iso 1'C4hydrocarbons"which comprises conf tat-,ting said fraction together with a secondC4 fraction V,obtained as hereinafter set forth witha for the production of butadiene therefrom, recovering butadiene from the products of dehydrogenation, subjecting the remaining :C4 hydrocarbons to anisomerizing treatment whereby a subthe isobutene contained therein is converted to normal butenes. and thereafter returning the isomerized C4 fraction to the'dehydrogenation treatment as said second C4 fraction.

The accompanying drawing illustrates sche matically twov process iiows which may be employed in accomplishing the objects of this in vention. e Figure l of the drawing illustrates a one stageoperation' in'which isomerization and dehydrogenation are Figure 2 illustrates a two stage operation in which dehydrogenation and isomerization are effected in separate zones, f Y Y Referring now to Figure l ofthe drawing, a C4' fraction which consistsrnot only of normal Ci hydrocarbons but also iso C4 hydrocarbons is supplied through line I to dehydrogenation and isomerizationzone 2 where it is contactedwitha catalyst at a temperature usually within the range of from'about"l00-l300 F. atv conditions suitable for effecting simultaneous isomerization. It1 is necessary in this yzone in order to prevent excess decomposition of the'butadiene to maintain a hydrocarbon partialpressure'of less than l atmosphere, preferably qfless than about300 mm.' mercury absolute. It is also desirable to employY relatively short contact timesv C4 butanes andbutenes at; conditions suitable effected in the same zone and dehydrogenation and which is formed, is not decomposed to secondary reaction products. The reaction may be conducted by passing the hydrocarbon vapors through a bed of granular catalyst, or it may be effected by flowing the hydrocarbon charge upward through a turbulent bed of powdered catalyst, the catalyst being kept in suspension by the upward flow of hydrocarbons therethrough. It is usually necessary also to provide some means of supplying heat to the dehydrogenation zone proper since the dehydrogenation reaction is strongly endothermic.

Catalysts which have been found suitable in effecting dehydrogenation include oxides of the metals of the left hand columns of groups IV, V and VI of the periodic table deposited on refractory supports. Usually the oxides of chromium, molybdenum, and vanadium deposited on alumina have been found to be superior. The preferred olefin isomerizing catalyst is a composite comprising a calcined precipitate of hydrous silica and hydrous alumina. Other suitable olefin isomerizing catalysts which have as their principal component an alkali free hydrous silica may also be employed andv will be described more fully later.

Several alternative methods of operation may be used in the catalytic zone. In cas an operation is employedin which the hydrocarbons are passed through a fixed bed of catalyst, several alternative methods of disposing the catalyst within the reaction zone may be employed. For example, the catalysts may be deposited in alternate layers throughout the depth of the bed, or the granules may be physically admixed so that a uniform distribution of both catalysts is obtained throughout the zone. On the other hand; it may be desirable to deposit the dehydrogenating oxide such as chromium oxide upon the isomerizing catalyst as a support. It is seen, therefore, that various methods may be employed for dispersing both catalysts throughout the reaction zone.

When powdered catalysts are used in the manner previously mentioned, either a mixture of powdered dehydrogenating catalyst with a pow- 1 dered isomerizing catalyst may be employed or the dehydrogenating oxide may be deposited upon the silica alumina hydrogel isomerizing catalyst, thereby producing a catalyst which will effect both reactions.

The products from catalytic zone 2 are then supplied through line l te butadiene separation zone wherein a separation is effected between butadiene on the one hand and a C4 fraction on the other. Also separatedin this zone are alight fraction comprising C3 and lighter products and a heavy fraction comprising C5 and heavier products. The butadiene separation step ordinarily consists not only oi' the necessary absorbers and stripper to make a separation between the C3, C4, Cs, fractions, but also of a distillation step or solvent extraction step, to make an efficient separation between butadiene and the other C4 hydrocarbons. At any rate, only the overall effect is shown on the drawing, Ca being recovered through line 5, rCr. through vvline 6, butadiene through line 1; and the remaining vC4 lfraction through line 8. The latter fraction is then Yreturned to dehydrogenation and isomerization zone 2 for further treatment.

Referring now to Figure 2 of the drawing, the C4 fraction feed is supplied through line 9 to dehydrogenation zone I0 wherein itis contacted with a dehydrogenation catalyst to produce butenes and butadiene. In this zone, groups IV, V,

CJI

and VI oxide catalysts may be used but the preferred catalysts comprise chromia, molybdena, or vanadia on refractory supports. Temperatures in this zone range generally from 1000 to 1300" F., and hydrocarbon partial pressures of less than 300 mm. mercury absolute are preferred. As in zone 2, either a granular catalyst in a fixed bed or a powdered catalyst in a turbulent bed may be employed. The products oi' dehydrogenation are Y supplied through line II to butadiene separation zone I2, similar to butadiene separation'zone 4 previously described in which a C3 and lighter fraction, a butadiene fraction, a C5 and heavier fraction, and a remaining C4 fraction are separated. The first 3 fractions are recovered through lines I 3, I4 and I5 respectively whilethe last named fraction is supplied through line I 6 to isomerization zone l1 wherein isomerization of the isobutene to normal butenes is effected. It should be noted that alternatively the fresh feed may be supplied to this point through line I8 in order to effect isomerization of the isobutene contained therein before subjecting the feed to a dehydrogenation reaction, unless the feed contains a high concentration of isobutene. However, the preferred introduction of thefeed is through line 9.`

Isomerization zone I] Vmay be of the fixed bed type employing granular catalyst or of the fluid bed typ employing powdered catalyst both of which types were previously mentioned in connection with zones 2 and I0. The temperatures in this zone range from approximately 750 to 1150 F'. or higher, although the preferred temperatures are of the order of about 1000 F. In order to maintain effective isomerization of isobutene to normal butene, it is essential that the basic constituent of the catalyst which is employed in this zone be a hydrous silica combined with either hydrous alumina, hydrous zirconia or both, to produce a. highly active catalytic mass that is thermally stable even at high temperatures. These synthetic catalysts may be prepared by forminga composite mass of silica hydrogel and alumina or zirconia hydrogel, followed by drying and calcining at 800-1500o F. It has been found that naturally occurring composites of silica and alumina are. not satisfactory for effecting the isomerization reaction and, furthermore, they are less thermally stable.

Isomerization products from zone I1 are supplied throughline I9 to C4 separation zone 20 wherein a separation is effected between Cs and lighter products, a C4 fraction, and C5 and heavier products. The Ca and C5 fractions are withdrawn through lines 2| and 22 respectively while the C4 fraction is returned to dehydrogenation zone I0 by way of line 23.

n The following example is intended to illustrate the operating conditions which may be successfully employed when conducting the two stage process as previously described.

A C4 fraction feed comprising approximately 40% oleiins and 60% parains, both normal and iso compounds being present, is dehydrogenated by contacting the vapors with a chromia-aluminia catalyst at a. temperature of approximately 1200 F., at an Vabsolute pressure of about 100 mm. of mercury and at a gas hourly space velocity of 300 measured at standard conditions. The resultant products of dehydrogenation are supplied to a separation zone in which butadiene is recovered by a combination of stripping, absorbing and azeotropic distillation. The C4 fraction remaining from the separation step is contacted at convert the isobutene contained isobutene contained and supplying the C4 products of the isomerization treatment to f 3. 'Ihe process of claim 1 furthercharacterized Y, asraeso afiempera'ture of about 1000 F. with a composite of lsilica and alumina prepared from the hydrogels of silica and alumina, in order to isomerize the isobutene containedtherein to normal butene.

The resulting C4 isomerized-fraction is returned to. the dehydrogenation zone for further conver-v Vsion into butadiene.

, I claim as my invention:

1. A process for `producing butadiene which comprises subjecting normal 'C4 hydrocarbons under; dehydrogenating conditions to the action 4 Aor a dehydrogenating catalyst to form butadienel with, the` accompanying amounts of isobutene, separating from the resultant vreaction products butadiene and a C4 iraction containing said' isobutene, contacting said C4 fraction With an oleiin isomerizing catalyst to thereininto normal butene'and supplying the C4 products of `-the Visomt-:rization treatment to dehydrogenating" 2.A process'for producing butadiene which comprises subjecting normal butenes under dehydrogenating conditions to the action of a dehydrogenatingcatalyst to form butadiene with ithe accompanying formationrof minor amounts of isobutene, separating from the resultant reac- A tion-products butadiene and 'a' C4 fraction containing said isobutenel contacting said C4 fraction v isomerizing catalyst to vconvert the therein into Vnormalbutene with an olefin the dehydrogenating step' in that said oienn isomerizin'g catalyst comprises v precipitated silica, precipitated alumina and prekcipitated zirconia. .ilhe process of Vclaim in that said olefin isomerizing catalyst comprises v` precipitated silica and precipitated alumina..

. The process of claim 1 further characterized in that said olei'ln isomerizing catalyst comprises yprecipitated silica and precipitated zirconia.

6. A process for producing butadiene which `comprises subjecting normalC4 hydrocarbons to the action of a dehydrogenating catalyst comprising alumina and chromia at a temperature of fromabout 1000 to about 1300 F. and a pressure below 300 mm. or mercury absolute isoform butaformation Vof minor ywith. an' olefin isomerizing catalyst' comprising 1 further characterized ing alumina and to isomerization to vconvert isobune, 'contacting said C4 -tion tothe dehydrogenating step.

diene with the accompanying formation of isobutene, separating from the resultant reaction prod-V ucts butadiene and a C4 fraction containing saidI fraction with an. oleiin isomerizingcatalyst comprising silica and alumina under olefin isomerlzing conditions to convert the isobutene contained therein into normai butene and supplying the C4 productsof the Y isomerization treatment to theidehydrogenating step. v

'7.' A process ior the action of a dehydrogenating catalyst comprischromia at a temperature of from about 1000 yto about 1300u F. and a pressure below 300 mm. of mercury absolute to form buta diene with the accompanying formation of isog v' butene, separating from the resultant reaction products butadiene and a C4 fraction containing said isobutene. vcontacting said C4vfraction silica'and zirconial under o lenndsomeri'zing con= ditions to convert the isobutene contained therein into normal butene and supplying "the C4 products of the isomerization treatment to the dehydro genating step. 8. In the deh drogenation of a normal C4hydrocarbon to produce butadiene; wherein isobutene is formed incidental to the production of butadiene, the method which comprises separat-V ing from the products of the dehydrogenating step. a butadiene fraction and a C4 fraction containing said isobutene, subjecting said C4 fraction butene, and returning the thus ytreated C4 frac- 9. The methodas denned in claim 8 further characterized in that said C4 fraction is subjected to isomerizationinl the presence of a catalyst comprising silica and alumina.

10. The method asY defined inV claim 8 furtherV f characterizedin that said C4 fraction is subjected 4 normal butene.`

to isomerlzation yin the presence of a catalyst comprisingsilica and zirconia. Y 11. The method as defined in claim 8 further characterized inv that said C4 hydrocarbon is a" producing -butadiensrmcnf comprises subjecting normal C4 hydrocarbons-to isobutene to normal 

